Eagle design

W0FMS wrote:
I think everyone would be
happy with U/L up and S/V down. That's probably the best compromise of
politics (U/V) and technology (L/S). I think that's what we should go with
on Eagle. For technical reasons, L/S should be primary and U/V secondary,
but the sat should be designed to have a power budget to run both
simultaneously.
Wayne replies:
U/L uplink and S/V downlink is the plan for Eagle, as presented at the 2002 AMSAT Symposium.
Downlink: Eagle doesn't allow for high-gain V-band antennas because the spacecraft is so small. So the primary "high gain" downlink would be S. The "omni" side of the spacecraft would have a V primary antenna, and presumably an S backup antenna.
Uplink: The "high gain" side of the satellite would definitely have U and L uplink antennas. The "omni" side would hopefully have both U and L patch antennas, with U presumably being primary if both receivers couldn't be left on all the time.
Power budget: I don't know if the power budget would support two transmitters for any length of time (I doubt it). So we can expect Eagle's primary downlink bands to be V near perigee and S near apogee. A fully functional power system would allow both receivers (U and L) to be on all the time. A wonderful aspect of the Eagle design is that there is no such thing as "bad sun angle" if all the solar panels are functional and the wings deploy properly.
I think it's a good design: Primary modes of UL/S near apogee, and UL/V near perigee, with a near-perigee backup mode of UL/S. The real beauty is that it's simple, small, and light. That makes it relatively affordable to build and launch. Maybe we could eventually have several of them in orbit. I'm writing this from memory, so I hope I haven't botched the modes too much...
Wayne Estes W9AE
Mundelein, IL, USA
p.s. The choice of U/V is no more political than the choice of microwaves. "Access through trees" and "access with small antennas" are both valid engineering considerations.
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